[gtk+] Update config.h.win32(.in)

[Chun-wei Fan <fanchunwei src gnome org>]

commit 6278c404510843782bda4ad9e44b19737c8af8cd
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Fri Aug 30 13:48:12 2013 +0800

    Update config.h.win32(.in)
    
    Define _GDK_EXTERN more in line with the definition of it on Windows as
    defined in configure.ac, and add a MinGW variant for it as well

 config.h.win32.in |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/config.h.win32.in b/config.h.win32.in
index 77b80aa..3ab9402 100644
--- a/config.h.win32.in
+++ b/config.h.win32.in
@@ -305,7 +305,11 @@
 /* #undef _FILE_OFFSET_BITS */
 
 /* defines how to decorate public symbols while building */
-#define _GDK_EXTERN __declspec (dllexport)
+#ifdef _MSC_VER
+#define _GDK_EXTERN __declspec (dllexport) extern
+#else
+#define _GDK_EXTERN __attribute__((visibility("default")))  __declspec (dllexport) extern
+#endif
 
 /* Define for large files, on AIX-style hosts. */
 /* #undef _LARGE_FILES */